Prior flow restrictors have been constructed by stacking a series of metal discs to which the flow restrictions have been imparted by processes such as chemical etching or electric discharge machining. The cost of these processes is relatively expensive, and the processes themselves are relatively slow. As the number of discs in a stack increased, a larger internal volume was required to accommodate the stack. Because the prior discs were metal, only limited temperature compensation for fluid viscosity effects across a large temperature range was possible. When it was necessary for the device containing the stack to have a parallel flow path, it had to be machined in another location, and this resulted in increased overall size.
The present invention relates to a new and improved fluid flow restrictor which possesses important advantages over prior ones. The fluid flow restrictor of the present invention is a unitary one-piece element that is adapted for fabrication using either metal or plastic. For instance, the element can be fabricated as an aluminum or zinc die casting, or it can be fabricated as an injection molded plastic. Where flow restrictors are required in several different models which handle several different flow rates, a single element can be tailored to the requirements of each particular model by an appropriate shearing operation. A flow restrictor of the invention can be adapted for laminar or turbulent flow, and thereby be adapted to embody the self-cleaning effect of prior flow restrictors. Because a flow restrictor of the present invention can be fabricated from any of numerous available materials, it is better adapted to compensate for temperature-induced fluid viscosity changes by appropriate selection of material. Where a device that incorporates a flow restrictor of the present invention requires a parallel flow path, such a path is readily incorporated as a through-hole passing through the core of the flow restrictor.